1. Field of the Invention
This invention relates to an electrophotographic photosensitive member utilizing a novel electrophotographic photosensitive material, more particularly to an electrophotographic photosensitive member incorporating a disazo pigment having a specific molecular structure in the photosensitive layer.
2. Related Background Art
Pigments and dyes exhibiting photoconductivity have been heretofore reported in a large number of literatures. For example, there is a report about photoconductivity of phthalocyanine pigments in "RCA Review" Vol. 23, p. 413-419, September, 1962, and electrophotographic photosensitive members employing the phthalocyanine pigments are disclosed in U.S. Pat. Nos. 3,397,086 and 3,816,118. Otherwise, as organic semiconductors to be used for electrophotographic photosensitive members, there may be included, for example, pyrilium dyes disclosed in U.S. Pat. Nos. 4,315,983 and 4,327,169, and "Research Disclosure" 20517, May, 1981; squaric acid methine dyes disclosed in U.S. Pat. No. 3,824,099; and disazo pigments disclosed in U.S. Pat. Nos. 3,898,084 and 4,251,613.
Such organic semiconductors can be synthetized more readily as compared to inorganic semiconductors, and also they can be synthesized as the compounds having photoconductivity to the light of the required wavelength region. An electrophotographic photosensitive member having a coating of such an organic semiconductor formed on an electroconductive support has the advantage of improved color sensitivity, but only a few are satisfactory for practical purposes with respect to sensitivity and durability.